The present invention relates generally to integrated circuit devices and, more particularly, to a piezoelectronic switch device for radio frequency (RF) applications.
A piezoelectronic transistor (PET) has been proposed as a low-voltage, high-frequency switch in which a gate voltage expands a piezoelectric (PE) transducer, generating a high pressure in an adjacent piezoresistive (PR) material which then transforms from semiconducting electrical behavior to metallic electrical behavior. The PET may be embodied as a 3-terminal device, or, with an intervening low-permittivity dielectric layer, as a 4-terminal device. The three and four terminal PETs are embedded in a material with high Young's modulus (HYM) to resist deformation. Logic circuits analogous to conventional complementary metal oxide semiconductor (CMOS) devices may be made from combinations of PETs as part of a new field of technology termed piezotronics.
In RF signal electronics, at frequencies above about 1 GHz, there is need for rapid switching between RF channels, such as for example in applications utilizing cell phone and radar technology while switching between different antennae, or tuning an antenna by switching between elements in a capacitor bank. In, for example, a cell phone application, microelectromechanical switches (MEMS) take up relatively large amounts of space, require high voltages (e.g., 30-80 V), have expensive hermetic packaging, limited endurance (e.g., 108-1010 cycles) and poor frequency response (e.g., 104-106 Hz). Thus, MEMS are not ideal for this type of application. On the other hand, semiconductor switches also have certain drawbacks such as, for example, poor isolation in an OFF state and large insertion loss in an ON state.
In general, ON/OFF switches have the well-known problem of, upon opening of the switch, such that as the circuit resistance R rapidly increases, the magnetic flux trapped in the circuit by its inductance L collapses on an ever-shortening time scale as the time constant L/R drops to zero, thus resulting in high induced voltages by Faraday's law and an undesirable RF voltage pulse, spark, or arc. Switches with no RF noise are useful in situations where RF quiet is required, such as airplanes during takeoff and landing, near sensitive radar and radio astronomical antennae, and in military settings. Switches that do not spark or arc are also useful in situations where there are volatile gases that could explode if exposed to a spark or arc. Arc-free switches also have greater endurance in that switch contacts are not damaged by arcing.